1. Field of the Invention
The present invention relates to an improvement in a process for the production of a 3-methyl-2-(4-halophenyl)butyronitrile.
2. Description of the Prior Art
3-Methyl-2-(4-halophenyl)butyronitrile is an important intermediate useful in the production of an insecticide developed recently, e.g., as disclosed in U.S. Pat. No. 3,996,244.
U.S. Pat. No. 4,012,428 summarizes in detail fairly recent prior art approaches toward the alkylation of phenylacetonitrile (e.g., as disclosed in Organic Reactions, 9, 297 (1957), J. Org. Chem., 37, 526 (1972), Tetrahedron Letters, 473 (1972), Roczniki Chem., 39, 1223 (1965) [Chemical Abstracts, 64, 12595 (1965)]and Roczniki Chem., 42, 1619 (1968) [Chemical Abstracts, 70, 37413 (1969)]and U.S. Pat. No. 3,996,244) and discloses an improved process for the production of a 3-methyl-2-(4-halophenyl)butyronitrile comprising reacting a p-halophenylacetonitrile with an isopropyl halide in an aqueous solution of an alkali metal hydroxide using, as a specific catalyst, a quaternary organoammonium salt. Even this process disclosed in U.S. Pat. No. 4,012,428 is, however, not always satisfactory industrially particularly from the standpoint of reproducibility.
Intensive investigations have now been made to discover a process for producing 3-methyl-2-(4-halophenyl)butyronitrile in a high yield and a high purity even on a commercial scale. Surprisingly it has been found that the reaction between the p-halophenylacetonitrile and the isopropyl halide to produce 3-methyl-2-(4-halophenyl)butyronitrile is adversely affected by p-halobenzyl alcohol and isopropyl alcohol which are inevitably present as by-products in the production of the p-halophenylacetonitrile and isopropyl halide, respectively. More specifically, p-halophenylacetonitrile is produced industrially by the reaction between the corresponding p-halobenzyl halide and sodium cyanide under alkaline conditions, which is accompanied by the by-production of p-halobenzyl alcohol due to the hydrolysis of the halogen attached to the benzyl moiety, and isopropyl halide is produced industrially by a halogenation of isopropyl alcohol or a hydrogen halide-addition to propylene, which is accompanied by unreacted isopropyl alcohol remaining or the production of isopropyl alcohol as a by-product, respectively.
No prior art is known including U.S. Pat. No. 4,012,428 which discloses that the alcohols inevitable present in the starting materials, p-halophenylacetonitrile and isopropyl halide, have an inhibitory effect on the reaction to produce 3-methyl-2-(4-halophenyl)butyronitrile therefrom. Accordingly, the production of the desired 3-methyl-2-(4-halophenyl)butyronitrile has been carried out using p-halophenylacetonitrile and isopropyl halide, both of which contain several % by weight of the corresponding alcohols, and, as a result, the desired product cannot be produced with good reproducibility. Large amounts of unreacted feed materials, by-products and decomposition products resulting from the low reactivity due to the inhibitory action of these alcohols complicate the subsequent purification process, and moreover, adversely influence the quality of the final insecticide produced therefrom as well as the insecticidal effect thereof.